COVID-19 triggered a rapid international shift toward online assessment, which has been accompanied by concerns about student cheating. If we aren't physically with students, how can we be sure they are completing tasks in the circumstances we require - and how can we verify their identity? This presentation explores what can be done to detect and deter cheating in online assessment. It argues that addressing cheating will require an uneasy balance between positive 'academic integrity' and adversarial 'assessment security' approaches.